I have seven bald cypress growing in my lawn. They have gotten old enough to put up knees. I have been just raising my lawn tractor deck and slowly letting the deck down to allow the mower blades to shave off the top of the knees. Over the winter the knees grew substantially and proliferated. What is the best way to rid the grass of these hidden hazards for the mower deck? Is it ok to just chop them out with an axe? I have dozens of of knees popping up at some distance from the trees.